The present invention relates to a novel sintered ceramic body based on or containing a titanium carbonitride or, more particularly, to a sintered ceramic body containing a titanium carbonitride and a metal boride and having excellent bending strength and hardness as well as outstandingly high density.
Titanium carbonitrides are promising as a material for various sintered ceramic bodies usable as a cutting tool, parts of heavy-duty machines and the like since the sintered ceramic body based on or containing titanium carbonitride is excellent in the high melting point, hardness and tenacity as well as the remarkable resistance against oxidation when used in a high temperature oxidizing atmosphere.
Notwithstanding the above mentioned advantages, titanium carbonitride-containing sintered ceramic bodies are currently not used in the industry at least as a refractory material because a sintered ceramic body prepared from a titanium carbonitride alone is relatively brittle and has an unsatisfactorily low bending strength while this problem of brittleness and poor bending strength cannot be overcome even by the attempts to admix one or more of additive ingredients to the composition to be subjected to sintering due to the counteracting adverse effects on the advantageous properties inherent to the titanium carbonitride. For example, titanium carbonitrides are useful as a matrix material of cermets as sintered with metallic nickel as a binder but such a titanium carbonitride-based cermet is defective due to the decreased resistance against oxidation and poor heat resistance as a result of admixture of the metallic nickel.
Therefore, it has long been desired in the technology of ceramics to develop a sintered ceramic body based on or containing titanium carbonitride and having high bending strength and hardness without suffering decrease in the resistance against oxidation and heat resistance.